The invention pertains to strobe units that emit high intensity pulses of radiant energy over wide viewing fields. More particularly, the invention pertains to a strobe unit intended to be mounted to an overhead surface and having a reflector, wherein a light source extends from the reflector, the reflector shaped and arranged to reflect light in vertical, oblique and horizontal directions.
High intensity strobe units for emitting pulses of radiant energy over large viewing angles are known. Such structures, for example, are disclosed in Moran U.S. Pat. No. 5,448,462, and Anderson U.S. Pat. No. 5,931,569.
While known units provide appropriate levels of visible radiant energy over wide angles, such as would be used to visually indicate a fire alarm, it would be desirable to be able to improve the efficiency of such units and reduce the electrical power required to drive such units. Reduction of electrical power, if achievable, is particularly important in that more strobe units can be driven from the same size power supply, using the same size distribution cables, than would heretofore be feasible.
In addition to reducing the amount of energy needed to energize a given unit, it would be desirable to provide as much light as possible, expanding the light output field without introducing undue complexity into the structure of the unit.
In accordance with the invention a strobe unit includes a reflector and a source of radiant energy, such as a light source, the source mounted close to the reflector. When the light source is energized by the electronic drive circuitry, it emits pulses of light which can be viewed by an individual in the vicinity of the housing. Additionally, the source emits light which is reflected by the reflector before being viewable by the individual. The reflector is intended to be mounted to a ceiling surface and is configured to reflect light effectively downwardly and radially to cover a 360 degree field.
The reflector has a plurality of reflecting regions arranged around the light source. The light source is preferably elongated in a first direction perpendicular to the mounting surface. According to one aspect of the invention, each reflecting region includes multiple reflecting sections. The sections include a partial parabolic section or surface extruded linearly substantially in the first direction, and a plurality of parabolic aiming sections or surfaces are extruded or projected linearly to a point at an acute angle to the mounting surface and arranged rotationally between partial parabolic sections of adjacent reflecting regions. The partial parabolic section is arranged to direct light radially outwardly and also in the first direction. The parabolic aiming sections are arranged to direct light from the light source generally obliquely to the first direction.
According to another aspect of the invention, each reflecting region can also include a planar or flat section or surface arranged adjacent to the partial parabolic section, between the partial parabolic section and the parabolic aiming sections, located within that region. The partial parabolic section and the flat section are located at a predetermined angle with respect to the elongated light source. The flat section can be planar and extend at an angle of about 65-75xc2x0 to the axis of the light source, 15-25 degrees relative to the mounting surface, and having its slope direction (line of maximum slope) parallel to, but slightly offset from, a radial plane that includes the central axis of the light source. The flat section reflects light out from the strobe unit in substantially the first direction and the radial direction.
According to a further aspect of the invention, each reflecting region can also include a raised parabolic aiming section spaced from the partial parabolic section and having a surface for directing light obliquely in a direction substantially toward the partial parabolic section, preferably in the compound 45xc2x0 direction .
The reflector reflecting regions can include four identical reflecting regions wherein the regions are contiguously positioned around a central axis. Preferably, the central axis of the reflector is co-linear with a central axis of the light source. Advantageously, each partial parabolic section has a height which is comparable to the length of the elongated light source. Each partial parabolic section is tilted slightly back from a radial plane that includes the central axis of the light source at an angle of about 2 to 3 degrees.
The light source is preferably located at a focal point of the partial parabolic sections. The parabolic aiming sections can be linearly projected obliquely to a point on, or near to, the central axis of the light source. The parabolic aiming sections can comprise differing partial parabolic surfaces arranged contiguously in a series. Each parabolic aiming section can be configured to reflect light at a selected range of angles, relative to a plane containing the central axis.
The parabolic aiming sections can be geometrically constructed by sweeping or projecting diminishing-size partial parabolic curves or cross sections linearly along lines of projection to an origin point on the central axis of the light source.
In an alternate embodiment, the reflector includes a partial parabolic section as described in the first embodiment. The reflector includes a hybrid reflecting region adjacent to, and generally perpendicular to, the partial parabolic section. The hybrid region is formed by a partial parabolic curve having its focal axis coincident with the central axis of the reflector and transitioning at its outer edge into an oblique radial line. The curve and line are rotated about the central axis to form a hybrid surface comprising a parabolic trough and a conical section. A parabolic aiming section is located adjacent to the hybrid region and is formed by a partial parabolic curve projected obliquely radially to the reflector origin, blended along its contiguous side into the hybrid region.
The reflecting regions of either embodiment each form a substantially L-shaped module with the partial parabolic section being an upstanding leg, and the parabolic aiming sections and/or the planar section being the respective generally perpendicular leg.
The strobe unit can include a ceiling-mountable housing. The housing includes a light output opening covered by a transparent lens. The reflector is mounted within the output opening, beneath the lens. Electronic drive circuitry can be carried within the housing. The elongated light source, which has first and second displaced ends along the central axis, can be mounted directly to the reflector, beneath the lens. A bulb holder can be arranged to support an outer end of the bulb. Reflecting surfaces of each of the reflecting sections can be formed by plastic walls coated with a highly reflective material.
When the bulb is energized, the strobe unit produces a light output profile that meets or exceeds outstanding UL requirements.
Numerous other advantages and features of the present invention will become readily apparent from the following detailed description of the invention and the embodiments thereof, from the claims and from the accompanying drawings.